1. Field of the Invention
The present invention relates to ferroelectric liquid crystal compositions and liquid crystal devices incorporating the composition.
2. Description of the Prior Art
Presently liquid crystal display devices predominantly utilize the nematic phase of liquid crystals, while active research has also been conducted in recent years on various display modes utilizing a smectic phase. Especially promising is ferroelectric liquid crystal display utilizing a chiral smectic C phase because this mode is adapted to large-capacity display with a wide viewing angle.
The liquid crystal material for use in the ferroelectric liquid crystal display device wherein the smectic C phase is utilized must of course exhibit the smectic C phase over a wide temperature range around room temperature and needs to fulfill various other requirements. First, the device for large-capacity display must have high-speed responsiveness, and from this view-point, the liquid crystal material needs to be highly amenable to spontaneous polarization and low in viscosity. Further to obtain satisfactory orientation and bistability when used for the liquid crystal cell, the liquid crystal material needs to exhibit the phase series of IAC (Isotropic-Smectic-A-Smectic C) or INAC (Isotropic-Nematic-Smectic A-Smectic C), and the helical pitch of nematic phase and smectic C phase needs to be sufficiently larger than the cell thickness. It is also desired that the material be great in tilt angle which is relevant to the contrast and brightness of liquid crystal display. The material must also be optimized in dielectric anisotropy, refractive index anisotropy, specific resistance, etc.
At present, however, it is impossible for a single compound to fulfill all the desired requirements, so that a plurality of compounds are usually mixed together for use as a liquid crystal composition. To prepare a liquid crystal composition fulfilling the requirements for actual use, it is necessary to use numerous single liquid crystal compounds having a wide variety of properties. It is even likely that compounds which per se exhibit no liquid crystal properties will be useful as components of the liquid crystal composition.